ATLANTA (AP) — Federal regulators are investigating whether workers at a factory that supplies parts to nuclear plants broke quality control rules and falsified records, according to regulatory filings.

A dozen workers at the Shaw Modular Solutions facility in Lake Charles, La., admitted to a manager that they sometimes entered the identification codes for other workers while recording who performed welds, according to the company's legal filings. The filings do not offer further details on the incident. The NRC would not comment on the ongoing probe, but its rules state that only a worker who performs a weld can document that it was completed, agency spokesman Scott Burnell said.

If true, the allegations do not necessarily mean that the factory's parts are defective or unsafe. But the allegations would represent a breakdown in the process intended to guarantee that parts installed in nuclear power plants meet strict standards to ensure safety. The case is being handled by the NRC's Office of Investigations, which probes allegations of wrongdoing.

The factory makes large parts destined for two nuclear power plants now under construction, Plant Vogtle (VOH'-gohl) in Georgia and Plant Summer in South Carolina. CB&I, which acquired The Shaw Group in February, said it is cooperating in the probe and has turned over all the requested documents.

"When CB&I first learned of the employee's concerns, we took immediate action," company spokeswoman Gentry Brann said in a written statement. "Today, the documentation issue has been corrected, and we have a full corrective action program in place to ensure this does not happen again."

The allegations are a setback for a factory that has been the subject of a large number of whistleblower complaints, struggled to meet production schedules and, according to analysts, had difficulty mastering the strict quality control process required in the nuclear power industry.

NRC officials requested information in October about the dozen workers who admitted they used other workers' codes, according to documents filed by company lawyers. The company told the NRC which workers were involved, but it initially resisted handing over other internal reports. The firm said it was concerned that the NRC might be forced to publicly release the documents, undermining the promises of confidentiality to company whistleblowers who report problems.

NRC commissioners voted April 2 to reject a request from Shaw to revoke the subpoena. The federal safety agency noted that the documents may be shielded from release under the federal open records act.

"We therefore do not expect such document requests to unduly burden, or otherwise create a chilling effect on, a facility's effort to promote a safety conscious work environment," the commission said in its order.

The company has been under scrutiny. Last month, the NRC proposed a $36,400 fine against Shaw for discriminating against an employee who raised a quality concern.

In addition, the NRC has accused Shaw of creating a workplace that discouraged employees at the Lake Charles factory from raising quality concerns. Federal officials said they received 19 allegations from people based at the factory from January 2010 to January 2013, more than a third of all vendor-related allegations received during that period.

"The NRC takes seriously the ability of employees to raise safety concerns without fear of retaliation, and employee protection from discrimination," said Glenn Tracy, director of the Office of New Reactors, in an April 18 letter to the company.

A survey conducted at the request of Shaw found that 27 percent of workers were not confident they could raise a quality concern without fear of retaliation. In addition, 30 percent of workers knew someone who suffered a negative reaction from management after raising a quality concern, according to federal documents.

Problems at the facility prompted the Atlanta-based Southern Co. to stop shipments of parts from the factory to its construction site at Plant Vogtle, southeast of Augusta. The utility and Westinghouse Electric Co, which designed the plants under construction in Georgia and South Carolina, have sent their own employees to monitor progress at the facility.

Southern Co. "has been in contact with the NRC to fully understand the issues," utility spokesman Mark Williams said in a written statement. The utility expects its contractors to cooperate with NRC requirements, he said.

SCANA Corp. spokeswoman Rhonda O'Banion said the company is confident in the quality of the components it received from the Shaw for the utility's new reactors in South Carolina.

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